1. Field of the Disclosure
The present disclosure relates to pressure reducers suitable for use in pressurized process lines and particularly useful for use in applications in which there is variable flow through the pressure reducer.
2. Description of the Background
Pressure reducers are used in pressurized fluid flow lines, such as process pipe lines in industrial plants, petro chemical refineries, chemical processing lines and the like, to dissipate pressure in a pipe, valve, or discharge outlet in a controlled manner for many various reasons. One common use of a pressure reducer is at an outlet point from a pressurized line to the atmosphere, such as in a high pressure steam line. In this instance, a pressure reducer is often used to avoid releasing steam directly into the surrounding air at a high pressure, which can produce unwanted noise if not controlled because of the rapid pressure drop between the line and the surrounding atmosphere.
A pressure reducer may be as simple as a restriction in a pipe line that is downstream from a valve or other operating point. Downstream restrictions in a pipe line are relatively inexpensive devices that can be used to add an additional pressure drop in a control valve or in a high-pressure pipe line, such as a pressurized steam line, that can reduce noise and vibrations. Unfortunately, fixed restrictions, such as diffusers, are often only effective for creating a desired pressure drop at one application condition (i.e., at a single flow rate and pressure drop) because the flow coefficient (Cv) of the diffuser is fixed. Any attempt to vary the Cv for different flow conditions, until now, has required the addition of complexity and cost by adding, for example, moving parts, such as plugs and springs.
In one exemplary application, a pressure relief outlet from a high pressure steam line is often provided with a conditioning valve to control release of steam from the line and to condition the steam to exhaust at a substantially lower pressure and temperature into the surrounding atmosphere than is present within the line. In such applications, it is also often desirable to reduce or substantially eliminate excess noise, such as whistling or hissing.
FIG. 1 shows one known conditioning valve 10 for a high-pressure steam exhaust that includes a pressure reducer 12 in the form of a canister with a cylindrical sidewall 14 and an end wall 16 covering the valve outlet 18 from a pressure relief valve 20. The end wall 16 is solid, and small holes 22 are disposed through the sidewall 14, which functions to dissipate energy from the steam and reduce the pressure of the steam on a downstream side 24 of the pressure reducer 12. The pressure reducer 12 is surrounded by a shroud 26, which directs the reduced-pressure steam through a cooling section 28 before being exhausted to the surrounding atmosphere. This type of pressure reducer is most effective in applications where there is a relatively constant or set flow rate through the small holes. However, the pressure reducer 12 is generally limited in effective use to one application condition because the pressure reducer only maintains a pre-selected pressure drop over a limited range of flow rates due to the static design of the area of apertures through which the steam can flow.
Another known conditioning valve 30 shown in FIG. 2 overcomes the above-noted limitation on flow volume by adding a plug 32 inside the pressure reducer 12 that is moveable along the sidewall 14 to expose more or fewer of the small holes 22 depending on the volume rate of flow of steam through the valve. A linkage 34 connects the plug 32 with a valve stem 36 such that the plug 32 opens and/or closes in parallel with opening or closing of a main valve plug 38. In this arrangement, the plug 32 is automatically adjusted to cover more of the small holes 22 at lower flow volumes and to expose more of the small holes 22 at higher flow volumes in response to movement of the main valve plug 38. Therefore, a relatively constant pressure drop may be maintained across the pressure reducer 12 across a larger range of flow volumes. Although this is an effective design to increase the effective operating range of the pressure reducer, the addition of moving parts presents different challenges to the design, installation, and maintenance of the conditioning valve 30.
The present inventor has attempted to overcome at least some of the limitations identified above with pressure reducers for use in variable process flow uses, as will become evident from the ensuing description. Of course, other uses, benefits, and advantages may also or alternatively be realized from the apparatus described herein.